1. Field of the Invention
The present invention to a power train which includes a prime mover in the form of an engine and a transmission which is operatively connected therewith and more specifically to a shift shock attenuation arrangement which varies the amount of torque produced by the engine during shifts and which features a sensor malfunction diagnostic function.
2. Description of the Prior Art
JP-A-58-77138 discloses an arrangement which sought to reduce shift shock by selectively varying the torque output of the prime mover during periods when the transmission is undergoing a shift.
However, this arrangement has proven only partially effective in that in the event of a sensor malfunction the shock attenuation function tends to be lost completely.
JP-A-62-88624 discloses an arrangement wherein in the event that one of an engine speed sensor, a throttle position sensor, a transmission output shaft rotational speed sensor and a torque converter turbine shaft rotational speed sensor, malfunctions, the sensor outputs are not used and the shift decision and engine torque variation control are generated in accordance with a timer.
However, this control tends to deteriorate shift shock attenuation and further tends to increase the rate of wear of the friction elements.